CN112803727A - Grid driving device and power conversion device - Google Patents

Grid driving device and power conversion device Download PDF

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Publication number
CN112803727A
CN112803727A CN202011019394.7A CN202011019394A CN112803727A CN 112803727 A CN112803727 A CN 112803727A CN 202011019394 A CN202011019394 A CN 202011019394A CN 112803727 A CN112803727 A CN 112803727A
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China
Prior art keywords
circuit
power supply
gate
switching element
switching
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CN202011019394.7A
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Chinese (zh)
Inventor
松原邦夫
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Fuji Electric Co Ltd
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Fuji Electric Co Ltd
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/16—Modifications for eliminating interference voltages or currents
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
    • H03K17/082—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit
    • H03K17/0822—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit in field-effect transistor switches
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/16—Modifications for eliminating interference voltages or currents
    • H03K17/161—Modifications for eliminating interference voltages or currents in field-effect transistor switches
    • H03K17/165—Modifications for eliminating interference voltages or currents in field-effect transistor switches by feedback from the output circuit to the control circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/28—Modifications for introducing a time delay before switching
    • H03K17/284—Modifications for introducing a time delay before switching in field effect transistor switches
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
    • H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
    • H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Provided is a gate driving device including: a drive circuit that drives a gate of a switching element connected between a high power supply potential section and a low power supply potential section in accordance with an input signal that instructs on/off of the switching element; a time storage circuit that stores a time from when the input signal is switched to the on command until a recovery surge voltage generated by a diode facing the switching element is detected; a switching determination circuit that determines whether or not to switch the gate drive condition of the switching element, based on a detected value of a power supply voltage between the high power supply potential portion and the low power supply potential portion; and a drive condition changing circuit that changes the gate drive condition in the current on period at the same time as the time stored in the time storage circuit in the previous on period, based on a determination result of the switching determination circuit.

Description

Grid driving device and power conversion device
Technical Field
The invention relates to a gate driving device and a power conversion device.
Background
Conventionally, an active gate driving method is known in which a switching speed is changed at an appropriate timing in accordance with a drain current or a collector current (hereinafter also referred to as a main current) flowing through a switching element in order to suppress a recovery surge voltage and reduce a switching loss. For example, patent document 1 discloses a gate drive circuit that stores a surge period from a timing of a turn-on command to a timing of recovery of surge voltage generation, and determines a timing of changing an effective gate resistance value of a switching element based on the surge period in the turn-on period stored last time in the turn-on period this time.
According to the description of patent document 1, the recovery surge voltage is reduced by increasing the effective gate resistance value during the surge period, and the switching speed is increased by decreasing the effective gate resistance value after the surge period has elapsed, so that the switching loss can be reduced. Further, according to the description of patent document 1, since the effective gate resistance value in the present on period is changed using the information in the previous on period, the time required for the feedback control can be made sufficient.
< Prior Art document >
< patent document >
Patent document 1: japanese patent application laid-open No. 4935266
Disclosure of Invention
< problems to be solved by the present invention >
Fig. 1 shows one example of an input signal for indicating on/off of a switching element connected between a high power supply potential portion and a low power supply potential portion, a voltage/current waveform of the switching element, and a voltage/current waveform of a reflux element opposite to the switching element. Id denotes a drain current flowing through the switching element, VDS denotes a voltage between the drain and the source of the switching element, IF denotes a forward current flowing through the reflux element opposite to the switching element, and VAK denotes a voltage between the anode and the cathode of the reflux element opposite to the switching element.
The power supply voltage supplied from the dc power supply (the power supply voltage between the high power supply potential portion and the low power supply potential portion) fluctuates to some extent due to some cause such as fluctuation of the input voltage of the dc power supply. Therefore, when driving the gate of the switching element connected between the high power supply potential portion and the low power supply potential portion, it is required to design so that the recovery surge voltage does not exceed the withstand voltage of the switching element connected in parallel with the reflux element even when conducting at the maximum power supply voltage.
Therefore, for example, as shown in fig. 1, it is considered that when the power supply voltage is reduced to the minimum value ed (min), even if the gate drive condition is not switched so that the gate resistance value is increased, the peak value Vp of the recovery surge voltage does not exceed the withstand voltage (element withstand voltage) of the switching element (see a circle a).
However, in the conventional technique of increasing the gate resistance value during each on period (reverse recovery period) in order to suppress the recovery surge voltage, as shown in fig. 2, the time change rate dI/dt of the main current Id often becomes gentle during each on period (see circle b). Therefore, when the power supply voltage is reduced with respect to the maximum value, the switching loss during the on period increases as compared with the case of fig. 1 in which the gate drive condition is not switched. Therefore, for example, there is a possibility that a reduction in power conversion efficiency and an increase in size of a cooling body for cooling the switching element may occur.
The present disclosure provides a gate driving device and a power conversion device, which can achieve both suppression of recovery surge voltage and reduction of switching loss even when power supply voltage fluctuates.
< means for solving the problems >
The present disclosure provides a gate driving device including: a drive circuit that drives a gate of a switching element connected between a high power supply potential section and a low power supply potential section in accordance with an input signal that instructs on/off of the switching element; a time storage circuit that stores a time from when the input signal is switched to the on command until a recovery surge voltage generated by a diode facing the switching element is detected; a switching determination circuit that determines whether or not to switch the gate drive condition of the switching element, based on a detected value of a power supply voltage between the high power supply potential portion and the low power supply potential portion; and a drive condition changing circuit that changes the gate drive condition in the current on period at the same time as the time stored in the time storage circuit in the previous on period, based on a determination result of the switching determination circuit.
In addition, the present disclosure provides a power conversion apparatus including: a plurality of switching elements connected in series between the high power supply potential portion and the low power supply potential portion; a plurality of gate driving devices provided for the plurality of switching elements, respectively, and driving a gate of a corresponding one of the plurality of switching elements; and a power supply voltage detection circuit that detects a power supply voltage between the high power supply potential section and the low power supply potential section, wherein each of the plurality of gate driving devices includes: a drive circuit that drives a gate of the corresponding one of the switching elements in accordance with an input signal indicating on/off of the corresponding one of the switching elements; a time storage circuit that stores a time from when the input signal is switched to the on command until a recovery surge voltage generated by the diode facing the corresponding one of the switching elements is detected; a switching determination circuit configured to determine whether or not to switch the gate drive condition of the corresponding one of the switching elements, based on the power supply voltage detected by the power supply voltage detection circuit; and a drive condition changing circuit that changes the gate drive condition in the current on period at the same time as the time stored in the time storage circuit in the previous on period, based on a determination result of the switching determination circuit.
< effects of the invention >
According to the technology of the present disclosure, it is possible to provide a gate driving device and a power conversion device that can achieve both suppression of recovery surge voltage and reduction of switching loss even when a power supply voltage fluctuates.
Drawings
Fig. 1 is a timing chart in the case where the surge suppression technique is not applied.
Fig. 2 is a timing chart in the case where the surge suppression technique is applied.
Fig. 3 is a diagram showing a structural example of the power conversion apparatus.
Fig. 4 is a diagram illustrating a structural example of the gate driving device.
Fig. 5 is a timing chart showing an example of the operation of the gate driver when the power supply voltage is high.
Fig. 6 is a timing chart showing an example of the operation of the gate driver when the power supply voltage is low.
Detailed Description
Hereinafter, embodiments according to the present disclosure will be described with reference to the drawings.
Fig. 3 is a diagram showing a structural example of the power conversion apparatus. The power conversion device 100 shown in fig. 3 is a device that converts dc input power into desired dc or ac output power by using a high-side (high side) switching element Q1 and a low-side (low side) switching element Q2. A load, not shown, is connected to a connection point M between the switching element Q1 and the switching element Q2. The power conversion device 100 includes a high power supply potential section 31, a low power supply potential section 32, a capacitor 30, switching elements Q1, Q2, a power supply voltage detection circuit 40, and gate drive devices 11, 12.
The high power supply potential portion 31 and the low power supply potential portion 32 are conductive portions that are connected to a dc power supply, not shown, and to which dc power is supplied from the dc power supply. The high power supply potential portion 31 is connected to the positive electrode P side of the dc power supply, and the low power supply potential portion 32 is connected to the negative electrode N side of the dc power supply. Specific examples of the direct current power supply include a rectifier circuit, a converter, a regulator, and the like. The low power supply potential portion 32 is a portion having a potential lower than that of the high power supply potential portion 31. A dc power supply voltage Ed is generated between the high power supply potential portion 31 and the low power supply potential portion 32.
The capacitor 30 is a capacitance element for smoothing the power supply voltage Ed, and a specific example thereof includes an electrolytic capacitor. The capacitor 30 has one end connected to the high power supply potential portion 31 and the other end connected to the low power supply potential portion 32.
The switching elements Q1 and Q2 are voltage-driven semiconductor elements, and each have a control electrode (gate), a first main electrode (collector or drain), and a second main electrode (emitter or source). Specific examples of the switching elements Q1 and Q2 include MOSFETs (Metal Oxide Semiconductor Field Effect transistors), IGBTs (Insulated Gate Bipolar transistors), and the like. Fig. 3 exemplarily shows a case where the switching elements Q1, Q2 are N-channel MOSFETs having a gate G, a drain D, and a source S.
The switching elements Q1, Q2 are connected in series with each other. The switching element Q1 is connected between the high power supply potential portion 31 and the low power supply potential portion 32, and is connected to the low power supply potential portion 32 via the switching element Q2. The switching element Q2 is connected between the high power supply potential portion 31 and the low power supply potential portion 32, and is connected to the high power supply potential portion 31 via the switching element Q1. The switching element Q1 has a gate G connected to the gate driver 11, a drain D connected to the high power supply potential section 31, and a source S connected to the drain D of the switching element Q2. The switching element Q2 has a gate G connected to the gate driver 12, a source S connected to the low power supply potential section 32, and a drain D connected to the source S of the switching element Q1. In the switching element Q1, a diode D1 is connected in antiparallel between the drain D and the source S. In the switching element Q2, a diode D2 is connected in antiparallel between the drain D and the source S.
The switching elements Q1, Q2 may be SiC (silicon carbide) or GaN (gallium nitride) or Ga2O3(gallium oxide) or diamond, etc. (wide band gap devices). By applying the bandgap device to the switching elements Q1, Q2, the effect of reducing the loss of the switching elements Q1, Q2 is improved. The switching elements Q1 and Q2 may be switching elements including semiconductors such as Si (silicon). Likewise, by applying the bandgap device to the diodes D1, D2, the effect of reducing the loss of the diodes D1, D2 is improved. The diodes D1 and D2 may be elements including semiconductors such as Si (silicon).
The power supply voltage detection circuit 40 detects the power supply voltage Ed between the high power supply potential section 31 and the low power supply potential section 32, and outputs the detected value Edd of the power supply voltage Ed to the gate driving devices 11 and 12, respectively.
The power supply voltage detection circuit 40 includes, for example, a voltage divider circuit including resistors 41 and 42, and isolation amplifiers 43 and 44 to which a voltage divided by the voltage divider circuit is input. The voltage dividing circuit divides the power supply voltage Ed by the resistors 41, 42, and supplies the voltages obtained by the division to the isolation amplifiers 43, 44, respectively. The isolation amplifiers 43 and 44 amplify the voltage signals supplied from the voltage dividing circuits, respectively, and output signals corresponding to the voltage values of the voltage signals as the detected value Edd of the power supply voltage Ed. The isolation amplifier 43 converts the power supply voltage Ed based on the low power supply potential portion 32 into a detection value Edd based on the source S of the switching element Q1, and the isolation amplifier 44 converts the power supply voltage Ed based on the low power supply potential portion 32 into a detection value Edd based on the source S of the switching element Q2. Since the input and the output of the isolation amplifiers 43 and 44 are insulated from each other, the common mode noise can be reduced.
The gate driving device 11 is provided for the switching element Q1, and drives the gate of a corresponding one of the switching elements Q1 among the plurality of switching elements Q1, Q2. The gate drive device 12 is provided for the switching element Q2, and drives the gate of a corresponding one of the switching elements Q2 among the plurality of switching elements Q1, Q2.
The gate driving device 11 is a driving circuit that supplies a positive or negative voltage to the gate of the switching element Q1 to turn on or off the gate of the switching element Q1. The gate driving device 12 is a driving circuit that supplies a positive or negative voltage to the gate of the switching element Q2 to turn on or off the gate of the switching element Q2. The high-side gate driver 11 drives the gate of the switching element Q1 by an active gate driving method of adjusting the switching speed of the switching element Q1 during the on period of the switching element Q1. The low-side gate driver 12 drives the gate of the switching element Q2 by an active gate driving method of adjusting the switching speed of the switching element Q2 during the on period of the switching element Q2. The gate driving device 11 operates with the source S of the switching element Q1 as a ground reference, and the gate driving device 12 operates with the source S of the switching element Q2 as a ground reference.
The gate driving devices 11 and 12 have the same structure as each other. Next, each configuration example of the gate driving devices 11 and 12 will be described with reference to fig. 4.
Fig. 4 is a diagram illustrating a structural example of the gate driving device. The upper arm gate drive device 11 is a drive circuit that turns on or off the gate of the switching element Q1 serving as an upper arm. The gate driving device 12 for the lower arm is a driving circuit for turning on or off the gate of the switching element Q2 as the lower arm.
The gate driving device 12 includes a driving circuit 50b, a surge detection circuit 90b, a time storage circuit 70b, a switching determination circuit 80b, and a driving condition changing circuit 60 b. Although not explicitly shown in fig. 4, the gate driving device 11 includes a driving circuit 50a, a surge detection circuit 90a, a time storage circuit 70a, a switching determination circuit 80a, and a driving condition changing circuit 60a, as in the gate driving device 12.
The drive circuit 50B is a circuit unit that drives the gate of the switching element Q2 in accordance with an input signal B from outside the gate drive device 12. The input signal B is a signal for instructing switching (ON) and OFF (OFF)) of the switching element Q2, and is, for example, a pulse width modulated signal (PWM signal). In the case where the input signal B is a PWM signal, it indicates an on command of the switching element Q2 when the input signal B is at an active level (e.g., high level), and indicates an off command of the switching element Q2 when the input signal B is at an inactive level (e.g., low level). The drive circuit 50b operates with the source S of the switching element Q2 as a ground reference.
The drive circuit 50a is a circuit unit that drives the gate of the switching element Q1 in accordance with an input signal a from outside the gate drive device 11. The input signal a is a signal indicating switching (ON) and OFF (OFF)) of the switching element Q1, and is, for example, a pulse width modulated signal (PWM signal). In the case where the input signal a is a PWM signal, it indicates an on command of the switching element Q1 when the input signal a is at an active level (e.g., high level), and indicates an off command of the switching element Q1 when the input signal a is at an inactive level (e.g., low level). The drive circuit 50a operates with the source S of the switching element Q1 as a ground reference.
Input signal a is a complementary signal with respect to input signal B. The input signal B is at an inactive level during a period in which the input signal a is at an active level, and the input signal a is at an inactive level during a period in which the input signal B is at an active level.
The surge detection circuit 90b detects a recovery surge voltage generated between the anode and the cathode of the diode D2 during the on period of the switching element Q1 opposing the switching element Q2. A voltage higher than the power supply voltage Ed generated between the drain D and the source S of the switching element Q2 (between the anode and the cathode of the diode D2) during the on period of the switching element Q1 is referred to as a recovery surge voltage generated by the diode D2 facing the switching element Q1. When detecting the recovery surge voltage generated by the diode D2, the surge detection circuit 90b outputs a detection signal S2 indicating that the recovery surge voltage generated by the diode D2 in response to the conduction of the switching element Q1 is detected.
The surge detection circuit 90a detects a recovery surge voltage generated between the anode and the cathode of the diode D1 during the on period of the switching element Q2 opposing the switching element Q1. A voltage higher than the power supply voltage Ed generated between the drain D and the source S of the switching element Q1 (between the anode and the cathode of the diode D1) during the on period of the switching element Q2 is referred to as a recovery surge voltage generated by the diode D1 facing the switching element Q2. When detecting the recovery surge voltage generated by the diode D1, the surge detection circuit 90a outputs a detection signal S1 indicating that the recovery surge voltage generated by the diode D1 in response to the conduction of the switching element Q2 is detected.
The surge detection circuit 90b observes, for example, a voltage VDS between the drain D and the source S of the switching element Q2. When the voltage VDS exceeding the set voltage value Va is observed, the surge detection circuit 90b outputs a detection signal S2 indicating that the recovery surge voltage generated by the diode D2 with the turn-on of the switching element Q1 is detected to the gate drive device 11. The surge detection circuit 90a observes, for example, a voltage VDS between the drain D and the source S of the switching element Q1. When the voltage VDS exceeding the set voltage value Va is observed, the surge detection circuit 90a outputs a detection signal S1 indicating that the recovery surge voltage generated by the diode D1 with the turn-on of the switching element Q2 is detected to the gate drive device 12.
The set voltage value Va is set to a value larger than the power supply voltage Ed and smaller than the maximum value (peak value Vp) of the recovery surge voltage that can be generated in design. The peak value Vp of the recovery surge voltage is, for example, a voltage value of a voltage VDS generated across the switching element facing the switching element when the switching element is turned on at a maximum value Ed (max) of the power supply voltage Ed. The surge detection circuits 90a and 90b can detect the occurrence of the recovery surge voltage at an intermediate stage before the recovery surge voltage reaches the peak value Vp by detecting whether or not the voltage VDS exceeds the set voltage value Va.
The surge detection circuit 90B determines whether or not the voltage VDS exceeding the set voltage value Va in the switching element Q2 is the recovery surge voltage generated by the diode D2 with the switching element Q1 turned on, using the fact that the input signal B is complementary to the input signal a, for example. Since the input signal B is complementary to the input signal a, the input signal a becomes an on command after the input signal B is switched to an off command. Therefore, the surge detection circuit 90B can detect the voltage VDS exceeding the set voltage value Va after the input signal B is switched to the off command as the recovery surge voltage generated by the diode D2 in accordance with the turn-on of the switching element Q1.
Alternatively, the surge detection circuit 90b may acquire the input signal a and detect the voltage VDS that exceeds the set voltage value Va after the input signal a is switched to the on command, as the recovery surge voltage generated by the diode D2 in accordance with the on of the switching element Q1. The surge detection circuit 90b may acquire the gate drive signal of the switching element Q1 instead of the input signal a. In this case, the surge detection circuit 90b detects the voltage VDS exceeding the set voltage value Va after the acquired gate drive signal is switched to on drive as the recovery surge voltage generated by the diode D2 with the switching of the switching element Q1.
Similarly, the surge detection circuit 90a determines whether or not the voltage VDS exceeding the set voltage Va in the switching element Q1 is the recovery surge voltage generated by the diode D1 with the switching element Q2 turned on, using the fact that the input signal a is complementary to the input signal B, for example. Since the input signal a is complementary with respect to the input signal B, the input signal B becomes an on command after the input signal a is switched to an off command. Therefore, the surge detection circuit 90a can detect the voltage VDS exceeding the set voltage value Va after the input signal a is switched to the off command as the recovery surge voltage generated by the diode D1 in accordance with the turn-on of the switching element Q2.
Alternatively, the surge detection circuit 90a may acquire the input signal B and detect the voltage VDS that exceeds the set voltage value Va after the input signal B is switched to the on command, as the recovery surge voltage generated by the diode D1 with the switching of the switching element Q2. The surge detection circuit 90 may obtain the gate drive signal of the switching element Q2 instead of obtaining the input signal B. In this case, the surge detection circuit 90a detects the voltage VDS exceeding the set voltage value Va after the acquired gate drive signal is switched to on drive as the recovery surge voltage generated by the diode D1 with the switching of the switching element Q2.
The surge detection circuit 90b includes, for example, a voltage division circuit that divides the voltage VDS by the resistors 92 and 93, and a transmission circuit 91 that outputs a detection signal S2 to the gate drive device 11 when the voltage value VDS exceeding the set voltage value Va is observed based on the voltage value obtained by the voltage division. The transmission circuit 91 outputs the detection signal S2 to the gate driver 11 via an insulating circuit including a magnetic circuit such as a coil. The surge detection circuit 90a also includes a transmission circuit 91 that outputs a detection signal S1 to the gate driver 12, as in the surge detection circuit 90 b.
The surge detection circuits 90a and 90b may detect the recovery surge voltage in a manner different from the manner of observing that the voltage VDS exceeds the set voltage value Va.
For example, when it is observed that the time rate dV/dt of change in the voltage VAK of the diode D1 changes from positive to negative, the surge detection circuit 90a outputs to the gate drive device 12 a detection signal S1 indicating that the recovery surge voltage generated by the diode D1 with the switching element Q2 turned on is detected. The voltage VAK of the diode D1 represents the forward voltage of the diode D1 or the voltage VDS of the switching element Q1. Similarly, when the time rate dV/dt of change in the voltage VAK of the diode D2 is observed to change from positive to negative, the surge detection circuit 90b outputs a detection signal S2 indicating that the recovery surge voltage generated by the diode D2 in accordance with the turn-on of the switching element Q1 is detected to the gate drive device 11. The voltage VAK of the diode D2 represents the forward voltage of the diode D2 or the voltage VDS of the switching element Q2. In the case of observing the time rate of change of the voltage VAK of the diode, as in the case of observing the voltage VDS, the surge detection circuits 90a and 90b determine whether or not the observed value is the recovery surge voltage according to the conduction of the opposite arm, and therefore, the input signal or the gate signal can be used.
The surge detection circuit 90b includes a transmission circuit 91 that outputs a detection signal S2 to the time storage circuit 70a of the gate driver 11. Similarly, the surge detection circuit 90a includes a transmission circuit 91 that outputs a detection signal S1 to the time storage circuit 70b of the gate driver 12.
The time memory circuit 70B stores a time Δ tb from when the input signal B is switched to the on command until the recovery surge voltage generated by the diode D1 facing the switching element Q2 is detected. The time storage circuit 70B stores, for example, a counter or a filter, a time Δ tb from an edge timing at which the input signal B is switched from the on command to the off command to a timing at which the detection signal S1 supplied from the surge detection circuit 90a of the gate driving device 11 is input. The time storage circuit 70B updates the time Δ tb every time the switching element Q2 is turned on (i.e., every time the input signal B is switched to the on command).
The time storage circuit 70a stores a time Δ ta from when the input signal a is switched to the on command until the recovery surge voltage generated by the diode D2 facing the switching element Q1 is detected. The time storage circuit 70a stores, for example, a counter or a filter, a time Δ ta from an edge timing at which the input signal a is switched from the on command to the off command to a timing at which the detection signal S2 supplied from the surge detection circuit 90b of the gate driving device 12 is input. The time storage circuit 70a updates the time Δ ta every time the switching element Q1 is turned on (i.e., every time the input signal a is switched to the on command).
The switching determination circuit 80b determines whether or not to switch the gate drive condition of the switching element Q2, based on the detection value Edd of the power supply voltage Ed. For example, the switching determination circuit 80 determines that the gate drive condition is switched when the detection value Edd is equal to or greater than a predetermined determination value ed (ref), and the switching determination circuit 80 determines that the gate drive condition is not switched when the detection value Edd is smaller than the determination value ed (ref). The determination value Ed (ref) is set to a voltage value (═ Ed (max) - α) between a maximum value Ed (max) and a minimum value Ed (min) of the fluctuation range that the power supply voltage Ed can withstand. α is a non-negative value. Similarly to the switching determination circuit 80b, the switching determination circuit 80a determines whether or not to switch the gate drive condition of the switching element Q1, based on the detection value Edd of the power supply voltage Ed.
The switching determination circuit 80b specifies a period (time Δ tb stored in the time storage circuit 70 b) for causing the driving condition changing circuit 60b to change the gate driving condition of the switching element Q2, based on the determination result of the presence or absence of switching of the gate driving condition of the switching element Q2. The switching determination circuit 80a specifies a period (the time Δ ta stored in the time storage circuit 70 a) for causing the driving condition changing circuit 60a to change the gate driving condition of the switching element Q1, based on the determination result of the presence or absence of switching of the gate driving condition of the switching element Q1.
The driving condition changing circuit 60b changes the gate driving condition of the switching element Q2 in the current on period of the switching element Q2 at the same time as the time Δ tb in the previous on period stored in the time storage circuit 70b, based on the determination result of the switching determination circuit 80 b. The driving condition changing circuit 60a changes the gate driving condition of the switching element Q1 at the same time as the time Δ ta in the previous on period stored in the time storage circuit 70a in the present on period of the switching element Q1, based on the determination result of the switching determination circuit 80 b.
The driving condition changing circuit 60b changes the gate driving condition of the switching element Q2 for a period designated by the switching determination circuit 80b (time Δ tb stored in the time storage circuit 70 b). The driving condition changing circuit 60a changes the gate driving condition of the switching element Q1 for a period designated by the switching determination circuit 80a (the time Δ ta stored in the time storage circuit 70 a). Although fig. 4 exemplarily shows the driving conditions a1 and a2 having different conditions, the gate driving conditions may be set to 3 or more driving conditions having different conditions.
The driving condition changing circuit 60b selects either one of the driving conditions a1 and a2 in accordance with the designation of the presence/absence time Δ tb. The driving condition changing circuit 60b selects the driving condition a2 at a time Δ tb designated by the switching determination circuit 80b, and selects the driving condition a1 at a time other than the time Δ tb designated by the switching determination circuit 80, for example. Similarly to the driving condition changing circuit 60b, the driving condition changing circuit 60a selects either one of the driving conditions a1 and a 2.
In the present on period, the drive condition change circuit 60b changes the gate drive condition to the condition for slowing down the on speed of the switching element Q2 at the same time as the time Δ tb in the previous on period stored in the time storage circuit 70 b.
The driving condition changing circuit 60b has, for example, 2 gate resistors having different resistance values, and a switching circuit for switching whether or not each gate resistor is connected to the gate of the switching element Q2. As for the resistance value of the gate resistance connected to the gate of the switching element Q2, the value thereof in the case of the selective driving condition a1 is smaller than the value thereof in the case of the selective driving condition a 2.
Therefore, while the switching element Q2 is turned on by the drive circuit 50b, the switching speed (on speed) of the switching element Q2 is slowed by selecting the drive condition a2 that increases the resistance value of the gate resistance. This can reduce the time rate of change (dI/dt) of the drain current flowing through the switching element Q2, and suppress the recovery surge voltage generated in the diode D1 in accordance with the conduction of the switching element Q2. On the other hand, while the switching element Q2 is turned on by the drive circuit 50b, the switching speed (on speed) of the switching element Q2 is increased by selecting the drive condition a1 in which the resistance value of the gate resistance is reduced. This can reduce switching loss during the on period.
The driving condition changing circuit 60b may have 2 gate current sources having different current values and a switching circuit for switching whether or not each gate current source is connected to the gate of the switching element Q2. As for the current value of the gate current source connected to the gate of the switching element Q2, the value thereof in the case of the selective driving condition a1 is larger than the value thereof in the case of the selective driving condition a 2. Alternatively, the driving condition changing circuit 60b may have a configuration including 2 gate voltage sources having different voltage values and a switching circuit for switching whether or not each gate voltage source is connected to the gate of the switching element Q2. As for the voltage value of the gate voltage source connected to the gate of the switching element Q2, the value thereof in the case of the selective driving condition a1 is larger than the value thereof in the case of the selective driving condition a 2.
Therefore, while the switching element Q2 is turned on by the drive circuit 50b, the switching speed (on speed) of the switching element Q2 is slowed by selecting the drive condition a2 that reduces the current value of the gate current. Thus, while the switching element Q2 is turned on by the drive circuit 50b, the time rate of change (dI/dt) of the drain current flowing through the switching element Q2 is reduced by selecting the drive condition a2 in which the current value of the gate current source or the voltage value of the gate voltage source is reduced. Therefore, the recovery surge voltage generated by the diode D1 in accordance with the conduction of the switching element Q2 can be suppressed. On the other hand, while the switching element Q2 is turned on by the drive circuit 50b, the switching speed (on speed) of the switching element Q2 is increased by selecting the drive condition a1 that increases the current value of the gate current. Thus, while the switching element Q2 is turned on by the drive circuit 50b, the switching loss during the on period can be reduced by selecting the drive condition a1 in which the current value of the gate current source or the voltage value of the gate voltage source is increased.
The switching determination circuit 80b determines whether or not to switch the gate drive condition of the switching element Q2, based on the detection value Edd of the power supply voltage Ed. The drive condition changing circuit 60b changes the gate drive condition in the current on period at the same time as the time Δ tb in the previous on period stored in the time storage circuit 70b, based on the determination result of the switching determination circuit 80 b. In this way, whether or not the gate drive condition is changed can be switched according to the magnitude of the power supply voltage Ed, and therefore, even when the power supply voltage Ed fluctuates, suppression of the recovery surge voltage and reduction of the switching loss can be achieved at the same time.
For example, when the recovery surge voltage generated by the conduction of the switching element is low due to the decrease in the power supply voltage Ed, switching to the gate drive condition in which the conduction speed of the switching element is slow can be prohibited. Thus, when the recovery surge voltage is reduced by the reduction of the power supply voltage Ed, it is possible to suppress an increase in the conduction loss due to the gradual change rate dI/dt of the drain current during the conduction period.
Similarly, the drive condition changing circuit 60a selects the drive condition a2 while the switching element Q1 is turned on by the drive circuit 50a, so that the time rate of change (dI/dt) of the drain current flowing through the switching element Q1 is reduced. Therefore, the recovery surge voltage generated by the diode D2 in accordance with the conduction of the switching element Q1 can be suppressed. On the other hand, the drive condition changing circuit 60a can reduce the switching loss during the on period by selecting the drive condition a1 while the drive circuit 50a turns on the switching element Q1. Further, the switching determination circuit 80a determines whether or not to switch the gate drive condition of the switching element Q1, based on the detection value Edd of the power supply voltage Ed. The driving condition changing circuit 60a changes the gate driving condition of the switching element Q1 at the same time as the time Δ ta in the previous on period stored in the time storage circuit 70a in the present on period, based on the determination result of the switching determination circuit 80 a. In this way, whether or not the gate drive condition is changed can be switched according to the magnitude of the power supply voltage Ed, and therefore, even when the power supply voltage Ed fluctuates, suppression of the recovery surge voltage and reduction of the switching loss can be achieved at the same time.
Next, with reference to fig. 4, 5, and 6, differences in operation of the gate driving device 10 due to the magnitude of the power supply voltage Ed will be described.
Fig. 5 is a timing chart showing an example of the operation of the gate driving device 12 when the detected value Edd of the power supply voltage Ed is equal to or larger than the determination value Ed (ref) (specifically, when the power supply voltage Ed has a maximum value Ed (max)). The description of the operation example of the gate driving device 11 is omitted because the description of the operation example of the gate driving device 12 is referred to.
The drive circuit 50B supplies a control signal (gate drive signal) to the control terminal (gate) of the switching element Q2 via the drive condition changing circuit 60B in accordance with the input signal B for switching the switching element Q2. In this example, the input signal B of high level represents an on command of the switching element Q2, and the input signal B of low level represents an off command of the switching element Q2.
When the input signal B is changed from the off command to the on command, the switching element Q2 starts to be turned on in accordance with the control signal input to its control terminal (time point t 1). The voltage VDS between the drain and the source of the switching element Q2 decreases while the drain current Id starts to increase.
Then, the time memory circuit 70B starts measuring the time Δ tb at the same time when the input signal B becomes the on command. For example, after the input signal B becomes the on command, the time storage circuit 70B starts counting with a preset count start value as a start point, and digitalizes the time Δ tb or the voltage value.
When the switching element Q2 starts to be turned on and the recovery surge voltage generated in the diode D1 is detected by the surge detection circuit 90a of the gate driving device 11, a detection signal S1 indicating that the recovery surge voltage is detected is output to the time storage circuit 70b of the gate driving device 12.
The time memory circuit 70b stops counting when the detection signal S1 supplied from the surge detection circuit 90a is input, stores the measurement value Δ t1 of the time Δ tb during the n-th on period, and outputs a signal indicating the measurement value Δ t1 to the switching determination circuit 80 b. Each time the switching element Q2 is turned on, the time storage circuit 70b stores the time Δ tb in the on period, and outputs a signal indicating the measurement value of the time Δ tb to the switching determination circuit 80 b.
Since the current detection value Edd of the power supply voltage Ed is larger than the determination value Ed (ref), the switching determination circuit 80b determines that the gate drive condition is switched. The switching determination circuit 80B specifies the drive condition a2 from a time t1 when the input signal B is changed from the off command to the on command to a time t2 when a measured value Δ t0 of the time Δ tb elapses. The measured value Δ t0 corresponds to the measured value of the time Δ tb in the (n-1) th on period obtained by the time memory circuit 70 b.
In other words, the gate driving condition is switched to the driving condition a2 from the time t1 when the on operation is started to the time t 2. Since the driving condition a2 is a condition in which the conduction speed is slowed down compared to the driving condition a1, the switching speed in the first half of the conduction period is slowed down, and the recovery surge voltage generated by the diode D1 is suppressed (see circle c).
However, after the measured value Δ t0 of the time Δ tb has elapsed, the driving condition changing circuit 60b returns the gate driving condition to the original driving condition a1 before the change. This increases the switching speed in the latter half of the on period, and reduces the switching loss.
At timing t3 when the input signal B is switched from the on command to the off command, the drive circuit 50B starts to turn off the switching element Q2.
The timings t5 to t7 in the (n +1) th switch correspond to the timings t1 to t3 in the nth switch described above. In other words, the switching determination circuit 80B specifies the driving condition a2 at a time point t6 when the measured value Δ t1 of the time Δ tb elapses from a time point t5 when the input signal B is changed from the off command to the on command. The measured value Δ t1 corresponds to the measured value of the time Δ tb in the n-th on period obtained by the time memory circuit 70 b. Time t7 corresponds to the timing at which input signal B changes from the on command to the off command.
On the other hand, fig. 6 is a timing chart showing an example of the operation of the gate driving device 12 when the detected value Edd of the power supply voltage Ed is smaller than the determination value Ed (ref) (specifically, when the power supply voltage Ed is the minimum value Ed (min)). The description of the operation example of the gate driving device 11 is omitted because the description of the operation example of the gate driving device 12 is referred to.
In this case, since the current detection value Edd of the power supply voltage Ed is smaller than the determination value Ed (ref), the switching determination circuit 80b determines not to switch the gate drive condition. The switching determination circuit 80b does not specify the driving condition a2 at the timing t 1. Thus, the gate driving condition in the on period is not switched to the driving condition a2, but is maintained at the driving condition a 1. Therefore, an increase in conduction loss due to a decrease in switching speed can be prevented. Further, even if the recovery surge voltage due to the lowering of the switching speed is not positively suppressed (see circle D), the recovery surge voltage generated by the diode D1 due to the lowering of the power supply voltage Ed is not so high. Thus, the recovery surge voltage generated by the diode D1 does not exceed the withstand voltage of the switching element Q1.
In other words, when the recovery surge voltage generated by the diode D1 is low due to a decrease in the power supply voltage Ed, switching to the gate drive condition that slows down the on speed of the switching element Q2 can be prohibited. Thus, when the recovery surge voltage is reduced by the reduction of the power supply voltage Ed, it is possible to suppress an increase in the conduction loss due to the gradual change rate dI/dt of the drain current during the conduction period. As described above, according to the technique of the present disclosure, even when the power supply voltage Ed fluctuates, both suppression of the recovery surge voltage and reduction of the switching loss can be achieved.
Here, since the magnitude of the recovery surge voltage changes according to the temperature of the diode, the switch determination circuit 80b may change the determination value ed (ref) according to the temperature of the diode D1 (which may include the ambient temperature of the diode D1). Accordingly, since whether or not the gate drive condition is changed is switched according to the temperature of the diode D1, it is possible to maintain both suppression of the recovery surge voltage and reduction of the switching loss even if the temperature of the diode D1 fluctuates. When the determination value ed (ref) is defined as "ed (max) - α", the switching determination circuit 80b changes the determination value ed (ref) by changing α. Similarly to the switch determination circuit 80b, the switch determination circuit 80a may change the determination value ed (ref) in accordance with the temperature of the diode D2 (which may include the ambient temperature of the diode D2).
For example, as shown in fig. 4, the gate driver 12 includes a temperature detection circuit 20b for detecting the temperature of the diode D2, and the gate driver 11 includes a temperature detection circuit 20a (not shown) for detecting the temperature of the diode D1. The temperature detection circuit 20a detects the temperature of the diode D1 by causing a constant current to flow through a diode provided in the vicinity of the diode D1 and measuring the forward voltage of the diode. The temperature detection circuit 20a may detect the temperature of the diode D1 by another detection method. The temperature detection circuit 20b also detects the temperature of the diode D2, as with the temperature detection circuit 20 a. The switching determination circuit 80b changes the determination value ed (ref) in accordance with the temperature detected by the temperature detection circuit 20 a. The switching determination circuit 80a changes the determination value ed (ref) based on the temperature detected by the temperature detection circuit 20 b.
The diode has a characteristic that the lower the temperature of the diode, the lower the recovery surge voltage. Based on this characteristic, the switching determination circuit 80b can make the determination value ed (ref) when the temperature of the diode D1 detected by the temperature detection circuit 20a is low higher than the determination value ed (ref) when the temperature of the diode D1 is high. Thus, for example, when the recovery surge voltage generated by the diode D1 is low due to a decrease in the temperature of the diode D1, switching to the gate drive condition in which the on speed of the switching element Q2 is slow can be prohibited. Thus, when the recovery surge voltage is reduced by the temperature decrease of the diode D1, it is possible to suppress an increase in conduction loss due to the gradual change rate dI/dt of the drain current during the conduction period. In the case where the determination value ed (ref) is defined as "ed (max) - α", the switching determination circuit 80b can increase the determination value ed (ref) by decreasing α. Similarly to the switching determination circuit 80b, the switching determination circuit 80a may set the determination value ed (ref) in the case where the temperature of the diode D2 detected by the temperature detection circuit 20b is low to be higher than the determination value ed (ref) in the case where the temperature of the diode D2 is high.
Although the gate driving device and the power conversion device have been described above with reference to the embodiments, the present invention is not limited to the embodiments. Various modifications and improvements such as combination with or replacement of a part or all of the other embodiments can be made within the scope of the present invention.
For example, the power conversion apparatus including at least one gate driving apparatus is not limited to a DC-DC converter that converts direct current into direct current. Specific examples thereof include an inverter that converts direct current into alternating current, a boost converter that boosts and outputs an input voltage, a buck converter that steps down and outputs an input voltage, a buck-boost converter that steps up or steps down and outputs an input voltage, and the like.
The surge detection circuits 90a and 90b may detect the recovery surge voltage in a manner different from the manner of observing the voltage VDS or the voltage VAK.
For example, when it is observed that the time change rate dI/dt of the drain current Id of the switching element Q2 changes from positive to negative, the surge detection circuit 90b may output, to the time storage circuit 70b, a detection signal S1 indicating that the recovery surge voltage generated by the diode D1 with the turn-on of the switching element Q2 is detected. Similarly, when the time change rate dI/dt of the drain current Id of the switching element Q1 is observed to change from positive to negative, the surge detection circuit 90a may output, to the time storage circuit 70a, a detection signal S2 indicating that the recovery surge voltage generated by the diode D2 with the turn-on of the switching element Q1 is detected.
Description of the symbols
11. 12 grid driving device
20b temperature detection circuit
30 capacitor
31 high power supply potential part
32 low power supply potential part
40 power supply voltage detection circuit
50b drive circuit
60b drive condition changing circuit
70b time storage circuit
80b switching decision circuit
90b surge detection circuit
100 power conversion device
Q1, Q2 switching element

Claims (11)

1. A gate drive apparatus comprising:
a drive circuit that drives a gate of a switching element connected between a high power supply potential section and a low power supply potential section in accordance with an input signal that instructs on/off of the switching element;
a time storage circuit that stores a time from when the input signal is switched to the on command until a recovery surge voltage generated by a diode facing the switching element is detected;
a switching determination circuit that determines whether or not to switch the gate drive condition of the switching element, based on a detected value of a power supply voltage between the high power supply potential portion and the low power supply potential portion; and
and a drive condition changing circuit that changes the gate drive condition at the same time as the time stored in the time storage circuit in the previous on period in the present on period, based on a determination result of the switching determination circuit.
2. The gate driving device according to claim 1, wherein the switching determination circuit determines to switch the gate driving condition when a detected value of the power supply voltage is larger than a determination value, and determines not to switch the gate driving condition when the detected value of the power supply voltage is smaller than the determination value.
3. The gate driving device according to claim 2, wherein the switching determination circuit changes the determination value in accordance with a temperature of the diode.
4. The gate driving device according to claim 3, wherein the switching determination circuit makes the determination value in a case where the temperature is low higher than the determination value in a case where the temperature is high.
5. The gate driving device according to any one of claims 1 to 4, wherein the driving condition changing circuit changes the gate driving condition to a condition that slows down an on speed of the switching element at a same time as the time in the last on period stored in the time storage circuit during the present on period.
6. The gate driving device according to claim 5, wherein the driving condition changing circuit decreases the on speed by increasing a resistance value of a gate resistor connected to the gate of the switching element.
7. The gate driving device according to claim 5, wherein the driving condition modification circuit reduces a current value of a gate current flowing through the gate of the switching element, thereby reducing the on speed.
8. The gate driving device according to any one of claims 5 to 7, wherein the driving condition changing circuit changes the gate driving condition to a condition for slowing down the on speed, and then returns the gate driving condition to an original driving condition before the change after the same time has elapsed.
9. A power conversion apparatus comprising:
a plurality of switching elements connected in series between the high power supply potential portion and the low power supply potential portion;
a plurality of gate driving devices provided for the plurality of switching elements, respectively, and driving a gate of a corresponding one of the plurality of switching elements; and
a power supply voltage detection circuit that detects a power supply voltage between the high power supply potential portion and the low power supply potential portion,
wherein the plurality of gate driving devices respectively include:
a drive circuit that drives a gate of the corresponding one of the switching elements in accordance with an input signal indicating on/off of the corresponding one of the switching elements;
a time storage circuit that stores a time from when the input signal is switched to the on command until a recovery surge voltage generated by the diode facing the corresponding one of the switching elements is detected;
a switching determination circuit configured to determine whether or not to switch the gate drive condition of the corresponding one of the switching elements, based on the power supply voltage detected by the power supply voltage detection circuit; and
and a drive condition changing circuit that changes the gate drive condition at the same time as the time stored in the time storage circuit in the previous on period in the present on period, based on a determination result of the switching determination circuit.
10. The power conversion apparatus according to claim 9, wherein the supply voltage detection circuit includes:
a voltage dividing circuit that divides the power supply voltage; and
and an isolation amplifier to which the voltage divided by the voltage dividing circuit is input and which outputs a detection value of the power supply voltage.
11. The power conversion apparatus according to claim 9 or 10, wherein the plurality of switching elements are wide bandgap devices.
CN202011019394.7A 2019-11-13 2020-09-24 Grid driving device and power conversion device Pending CN112803727A (en)

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